Automatic selecting system.



FLSGHOENWOLP.

AUTOMATIC SELECTING SYSTEM.

APPLIOATION FILED MAY 6, 1907.

988,390. Patented Apr. 4,1911.

3 SHEETS-SHEET 1.

1 I T V P. SCHOENWOLF.

AUTOMATIC SELECTING SYSTEM.

APPLICATION FILED MAYG 1907 Patented Apr, 4, 1911.

3 SHEETS- SHEET 2.

P. SCHOENWOLF. AUTOMATIC SELEGTING SYSTEM.

APPLIUATION FILED MAY 6, 1907.

988,390. Patented Apr.4, 1911.

3 SHEETS-SHEET 3.

with switch wipers adapted to move from UNITED STATES PATENT OFFICE.

FRED SCHOENWOLF, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO A KELLOGG SWITGHBOARD & SUPPLY COMPANY, A CORPORATION OF ILLINOIS.

AUTOMATIC SELECTING SYSTEM.'

Specification of Letters Patent.

- Patented Apr. 4., 1911.

Application filed Mayfi, 1907. Serial No. 372,257.

To all whom it may concern:

Be it known that I, FRED SGHOENWOLF, a citizen of the United States, residing at Chicago, county of Cook, and State of Illistance, switches comprising a series of sets of adjacently-disposed stationary contacts contact set to contact set. Such an arrangement In a telephone system would ordinarily comprise two talking wipers carrying the talking connections and a private or test wiper having test means associated with it to enable it to pick out a'set of idle contacts through which a talking circuit may be completed. In such structures, it is customary to provide thetest' wiper with an end sufficiently broad so that it may engage a second contact before leaving-the one previously engaged by it, while the talking wipers are preferably narrow at their contact extremities so as not to engage the'next contacts until after they have left the ones previously engaged by them. This, of course, is to prevent the possibility of the talking wipers being left in an intermediate positionengaging contacts of two talking'circuits.

In the systems to which I-have more specifically applied my invention, the selector 7 switch is provided with an operating. relay which, when the switch is traveling, is connected to thepri'vatewiper, the said wiper moving from contact to contact, holding the relay energized. as long as it is passing overcontacts connected to one side of the battery; As soon as .a contact, not thus connected, is reached and the private wiper switch, it may happen that the switch wipers will stop at a time when the prlvate wiper has left the last busy contact and before the talking'wipers have moved sufli- I ciently to engage the talking contacts corresponding to the idle contact found by the private wiper. It will be understood that' in theuse of spring-restoring switches, such troubles are of less probability because a retaining pawl there ordinarily operates upon a ratchet and will, in case of such a half step, fail to engage the next tooth of the ratchet,'and the spring will then restore the switch back to the preceding contact set.

As before indicated, my invention is for the purpose of preventing the difliculties above mentioned and in the preferred embodiment of my invention,as applied to a.

magnet, I provide switch havinga drivin two operating circuits or the magnet; one, which may be called a primary clrcuit, being controlled by a front contact of an operating relay; the other, which may be called a secondary circuit, including a back contact of the operating relay and what relay allows the closing of the bak'contact' included in the secondaryoperating circuit of the magnet. v

Referring now to the drawings, I show in Fig. 1 a simple automatic selecting sys- 1 'tem, as applied to a semi-automatic telephone exchange employing-two switches of varying characters, in the arrangement of each of which my invention has been in-' cluded; Figs. Qand 3 are respectively top and side views of a.sele ctive switch inechanism that may be employed in connection. with the circuit of Fig. 1; Fig. ishows the private wiper of' the switch and its. contacts; and Fig. 5 shows an auxiliary wiper of the switch and its contacts..- f

Referring first to Fig. 1, I show at A and C, respectively, two subscribers lines of well-known character, and at D, E, F and H, the exchange instrumentalities for inthem. The apparatus at ter connecting D- 1s an operators cord c1rcu1t,

while that at H is a B operators cordcircuit. The apparatus for establishing a connection between the cord-circuit l) and the cord-circuit H includes a springjack j comprised of the-contacts 1-1 and 22, multiple terminals .46, 48 and 50 pertaining to said jack, and a number of selecting switches, one of which, E, is shown including the wipers 47, 49, 51 and 53. The selector switches such as F are normally at rest and an idle one is started through the instrumentality of the distributer switch E.

having its circuits in operative relation with the jack j. Each A operator will have a number of cord-circuits such as D, and a number of jacks such as j. The terminals 46, 48 and 50 of the springjacks would be grouped together before the wipers of the switches F, it being understood that each switch F pertains to a link-circuit including conductors 85 and 86 extending to a cord-circuit similar to H. The jacks may or may not be multiple jacks, although I havev shown at one multiple for the jack The distributer switch shown at E includes the differential relay 34 controlling the starting relay'35 which is placed in operative relation with idle switches F through its armature, the wiper 36 and the contacts 38. Included in the switch E is also the operating relay 43 with its winding connected to the test wiper 37, arranged to sweep over the contacts 39 of the different switches F, the said relay 43 being thereby rendered sensitive to the idle or busy conditions of such switches so that when the switch E is once started, it will continue its travel until the test wiper 37 engages the contact 39 of an idle switch. lVhen relay 43 is operated, the driving magnet 42, controlling the switch wipers 40, 37 and 36, receives successive current impulses from generator G to ground through the attracted armature 44. The strip 41 is provided with a series of projections adapted for successive engagement by the auxiliary wiper 40. The wipers 40 and 37 may conveniently be placed one above the other on a rotary shaft, and the contact projections of the strip 41 extend intermediate of the different test contacts 39 of the selectors. If the switch E, under the influence of magnet 42, moves its wipers one full step, the wipers 40, 37 and 36 will be moved a full step so that wiper 40 will be resting free of thestrip 41 and between two projections,

while wipers 37 and 36 will be moved a full step to engage the next contacts 39 and 38. If, as before indicated, the wiper 37, having engaged an idle contact 39, opens circuit through relay 43 and the said relay retracts its armature 44 so quickly that magnet 42 cannot complete its armature stroke to drive the wipers the full step, then wiper 36 may be intermediate of two contacts 38 so that when the switch E is to be again used to start an idle selector, the ()JQl'fltlOIl of its starting relay 3.) will be inet'ective because the wiper 36 will be on open circuit. As the initiation of travel of the switch E is ca pendent upon the starting of the switch F, it will be obvious that in such case as that just described, the switch E might be rendered inoperative. This would be especially undesirable in the master-switch, inasmuch as it would ordinarily be common to a large number of circuits, for starting the switches to select them, and all the circuits would be rendered useless until the trouble was detected and rectified. In the structure 'at E, however, the wiper 40 and the contact projections of 41 are effective, if relay 43 is, as indicated, prematurely deenergized, to cause another impulse to flow from generator G through magnet 42, wiper 40, the intermediately positioned projection of 41, and to ground through the back contact of armature 45. This additional actuation of magnet 42 does not move the switch wipers a full step, but merely causes them to complete this step already partially made, because the armature-driven pawl of mag net 42, as will be understood from the hereinafter given description of Fig. 2, will engage the same tooth of its associated rotary ratchet as that engaged by it when it made the false move and will drive the switch only a partial step. Of course, on the completion of the second actuation of magnet 42, wiper 40 will have been brought to a position between two projections of 41 and no further actuations of magnet 42 will be produced.

The switch at F, for selecting the jacks at the A operators position, may comprise an operating relay OR, a driving magnet 59 controlled by said operating relay, the

said magnet being controlled over a primary circuit including the front contact of armature 57, and over a secondary circuit includ ing the back contact of armature 5G and the wiper arranged to engage one of the projections of the strip at all times except when the private wiper 47 and the talking wipers 49 and 51 are resting substantially squarely upon one of their contact sets; the arrangement being in a general way similar and adapted to serve the same ends as the arrangement at the distributor switch E. In the operation of the switch F, the relay OR, initially operated over wiper 36 and contact 38 at switch E, is by armature 56 operatively related to the test wiper 47 so as to be sensitive to the normal or altered electrical conditions of the private contacts 46 pertaining to the different springjacks The oft-normal switch spring ON controls the off-normal relay ONE, which latter has contacts for controlling the circuits of the distributer switch E after the switch F is started. The release relay RR is provided to cause the return of the Switch F to normal by causing travel thereof in the direction in which it Was initially operated to a zero point.

To describe Fig. I and its operation in detail, and assuming that the subscriber at A desires his line connected tor conversation with thatsof the subscriber at C, the subscriber at A removes his receiver from the hook-lever a which then bridges the transmitter and the primary of the induction coil across the two limbs ofthe line, the upward movement of said lever a also operatively dissociating the call-bell from the line limbs in the well-known manner. A circuit for direct current is thereby closed from battery B through line relay 1, normal contact of relay 2, lever 11 and its alternate contact, returning through the upper armature of relay 2 and to ground, energizing relay 1 to display lamp L. The operator, observing the signal, inserts the answering plug into the answeringjack of the subscribers line, closing contacts and 63 and a path for current from battery B, sleeve relay 8, contact G3, cut-ofi relay 2 to ground, the cutoff relay attracting its armatures to operatively extend the line limbs to the springjack contacts. The resulting energization of relay 8 would display supervisory. lamp 9, were not relay 7 .at this time operated by current from ground over contact through the substation, returning through contact 3 6 and relay 8 to battery. The operator, depressing levers 14c and 'l5,bridges her telephone in circuit and learns the exchange of the subscriber wanted. The jack j'is assumed to be a jack having a circuit adapted to be selected by a selector F forming a terminal of a trunk line leading to the exchange wherein the called subscribers line terminates. If the same be considered a multiple jack which, as before indicated, it may or may not be, the A operator will first touch tip 20 to sleeve 21 of the jack, which sleeve, if it pertains to an idle jacln'will be grounded through armature 29 and relay 23, 'withoutthere being any connection to the active side of battery at said springjack. In such case, the test relay 13, connected with tip contact 20 of the plug, being also grounded, no flow of current throughsaid relay occurs and its armature remains inert, no click being then caused in the oper ator s telephone receiver. If, howex'er, the jack j be busy, another cord-circuit plug will have been inserted in a multiple thereof, producing a potential other than groundat the sleeve 21, in which case test relay 13 will be operated and a elick caused in the operators receiver.

Assuming the jack' 7' to be idle, the operator inserts thc'calling plug therein, closing contacts 2022 and 1921, whereupon cur rent flows from battery 13, relay 11, normal contact 17, contact 19-21, armature 29, relay 23 to ground, operating relay 11 to close acontact in the tip talking strand of the cord, and relay 23 to attract armature B t, closing circuit from ground through armature 2 4, resistance 1", over common conductor 30, leftwinding of relay 3% to battery B, operating relay 34, whose attracted armature energizes starting relay 35, whose attracted armature completes a circuit from ground, contact 36-38, armature of relay ()NR, operating relay OR, to battery B. Relay OR is energized, attracting armature 57 and causing a current impulse to flow from generator Gr, through magnet 59, said armature 5? to ground, the magnet being thereby actuated to drive the wipers of the switch F a step to engage their respective first contacts- L6, 4:8 and 50. Armature 56 of the operating relay provides a locking circuit for relay OR extending through wiper at? and through the first contact 46 to ground over a'conductor 8-1, the back contact of an armature 27, the back contact of an armature 2st to ground, of a springjack circuit similar to that of jack j, itbeing understood that any convenient or desired number of multiple terminals of jack on euits similar to that of may be associated with the Switch, As long as such jacks are idle, their relays 23 and 26 will be unoperated'and therefore ground connections similar to that before described will be found at the successive contacts 4L6 engaged by wiper 47 as the switch F travels over contacts of idle jacks that is, jacks in which an oper-.

ator has not inserted a plug; Thus relay OR will continue locked over wiper 4L7 and successive contacts -16 to successive grounded armaturcs 2i, holding its armature $57 attracted, successive impulses from generator G flowing through magnet 59, the switch being thus driven step by step until the wiper 47 engages the contact #16 ot' a calling jack. The relay 23 of said jack being oper ated "as before described, the armature 2st will be attracted and its multiple contact s; hence ungrounded; relay OR'thereitore hecomes denergized, and the pulsations cease through magnet {59; wipers 47, 49 and 51 then remaining upon the multiple contacts of the selected spring-jack j, while wiper 53 will be between two projectiom: of strip Inasmuch as switchessuch as that shown at F and'in Fig. 2 maybe operated at a speed up to sixty or more steps per second, it will be readily understood that the relay OR must, when its circuit is opened, allow the retraction of its armature 57 in a very small space of time; and as wiper 47 preferably leaves a contact 46 after engaging its successor' before the wipers 49 and 5t engage the corresponding talking contacts, the relay OR may be denergized and out oft the imare spaced intermediate of the private conthrough contact 39 tacts 40, will be engaged by the wiper53; and on the de'energization of operating relay OR, an impulse will low from generator G through magnet 59, wiper 53 and a projection, back contact of armature 5G to round,

' causing to be again actuated, as it were,

traction of its armature,'thus stepping the switch wipers the remaining uncompleted distance to the operative position beyond that one at which they last were. It will be noted that armatures 55 and 58 ofrelay OR are attracted while the switch is operated, the talking wipers 49 and 51 being thus on open circuit while the switch is traveling.

When. the switch F makes its first step, spring ON is shifted to engage its contact, operating off-normal relay ONR, whose left armature operatively disconnects relay OR from the starting wiper. 36 so that, until restored to a normal position, it is free from the influence ot the distributer switch E. Armature (32 completes a circuit from ground through armature (30, front contact of armature Gi resistance r and the right winding of relay 34: to batteryB Circuits are now closed through both windings of relay 34, which windings are differentially disposed; and since the resistances r and 1". are equal, the core of relay 3 1 is neutral and its armature is retracted, opening circuit through starting relay 35, whose retracted armature takes ground from starting wiper 36 so that it is on open circuit while the distributer switch E is traveling. The attracted armature 03 of relay ONR initiates travel of switch E by closing circuit from ground 37, operating relay 43 to battery B, whereby the armatures of re- -lay 43 are attracted, armature 44 closing a circuit for a current impulse from generator G, operating magnct'al, to ground. The

-10, 37 and 3G a step, wipers 37 and36 engaging the contacts 39 .and 38 of the next p p 1 switch I and 1f? this is a busy su itch, relay 513 will be locked through. attracted armature 63 of its off-normal relay ONR', a second impulse flowing through magnet 42,

causing a second step of the switch, and successive locking circuits for relay will be established through wiper 37 and successive contacts 39 until a contact of a switch F is encountered, which switch is at normal and has its ott-norn'ial relay ONR therefore decuergized. In such case, owing to the retracted condition of armature 63, relay 13 is'deenerglzed and its armature 1s retracted,-

first actuation of magnet 4:9 moves wipers opening circuit through magnet 42. it the last actuation of magnet 1-2 produced a full step of the switch, then wiper 10 will be intermediate of two projections of strip 411. If, however, the last step is a partial step the character hereinbet'ore described, then on the retraction of armature 45, a current impulse will flow from generator G through magnet L2, wiper 10 and a projection of 41 to ground at the back contact 45, causing magnet 42 to again attract its armature, its pawl engaging the same toot-h of the switch ratchet previously engaged by it and completing the step of the wipers.

It is assumed that the switch F has now selected the contacts 46, 48 and 50 pertaining to the particular jack 7' in which the operator at D has inserted the calling plug of her cord. -As soon as this'selection was hiade as previously described, on the deenergization of relay OR, a current flow took place from battery B, through sleeve supervisory rela 1]., through 17, 19, E21, 25, 33, 50'51, 58, re ay RR, relay 70, to ground, operating relay 11 to display supervisory signal 12, and relay at H to display call signal lamp 87. Relay 25 is actuated and attracts its armature to close circuit through relay 26 which is thereupon energized, its armature 28 closing a normally open contact in the talking circuit of conductor 33, which 'now short-circuits relay 25, causing its deenergization. Armature 27 is attracted to complete a locking circuit fol-relay 26 over conductor 31, contact 4t 647, and to ground through back contact of armature 56. It will be noted that as soon as relay OR was 'deenergized on selection made, a ground was connected at retracted armature 56 through wiper 17 to the multiple contacts t646 of the selected jack, whereby the said terminals will tcst busy to any other switch F. Attracted armature 29 of relay 26 opens the circuit of relay 23, which relay is deenergized, and circuit through the left winding of relay 34: is opened vat the armature of said relay-23. The before-described currcnt flow through relay RR attracted. the relays armature, energizing relay 54, whose attracted armature ('30 opens the circuit through resistance r and the right winding of relay 34 at substantially the same time that circuitis opened through the lett winding, so that the relay 3-l is not lOl sistances r and 1" will be unavailing on account of the other resistance W or rm still Armature 6l'of relay 54, when the relay is energized, locks the said relay to ground at ofi"--normal spring ON so that relays ONE and are now both locked through the said spring and so remain until the conclusion of conversation and the return of the switch F to normal. The B operator at H now depresses levers 78 and 79 of her listening-key and inquires of subscriber A t-he number of the line wanted, into a springjack of whose line she inserts the plug of the cord-circuit H, closing contacts 84-3 and 8 34, provided the preliminary test, which she makes in the manner similar tothat in which the operator D tested the jack y', has indicated to her that the line wanted is idle. Upon the insertion of the plug, current flows from battery B through sleeve supervisory relay 74, through 81, 843, cut-ofi' relay 2 to ground, operating the cut-oil relay and connecting the line limbs to the jack contacts 3 and 4 respectively. The operated relay 74 closes a normally open contact in the tip talking strand, and attracted armature puts out lamp 87 and would cause the display of supervisory signal 73 were not relay 70 at this time energized. The operator now throws over levers and 81, including ringing generator 82 in circuit with the called-tor. line,current passing therefrom through the attracted upper armature of relay 2, the condenser and call-bell at the substation, returning to the attracted lower armature of relay' 2 and throngh'lever 81 to ground. The operator then restores her ringing-key levers and the called subscriber O, removing his receiver from the hook-lever, allows the elevation of hook-lever a, closing a low resistance circuit from ground, through relay 65, attracted right armature of relay 74, contact 80, contact 83-4, through the transmitter and induction coil at the substation,lever a, returning through contact 3-84 and relay 74 to battery. Relay 65 is thereby operated and, by attracting armature 66, puts out the calling supervisory signal 68, actuated, on

the attraction of armature 75 of relay 74, by

current from ground through said armature, armature 66 and its normal contact. On the extinguishing of lamp 68, the B operator at H knows that the call has been answered. The attraction of armature 67 of relay 65 completes a path for the flow of current from battery B through the inductive resistance coil 69, armature 67, to the left over conductor 85, contact 49-48, conductor 32, plug and jack contact -2220, normal contact 16,

attracted right-hand armature of relay 11, supervisory relay 10 to ground; which relay 10, being energized, attracts its armature and puts out calling supervisory lamp 12,

the A operator thus knowing that the call has been answered. The two subscribers A and O are now in conversation, battery being supplied to the transmitter of subscriber A through the windings of relays 7 and 8,

while battery is supplied-to the transmitter of subscriber O through thewindings of relays 65 and 74; the talking circuit being traced through the exchange by the heavily- .marked conductors, condensers m and 'n being included inone side of the talking circuit, and 0. and being included in the other side of the talking circuit.

Subscriber A, at the conclusion of con-- vqrsatioin'replaces his receiver, opening circuit through relay 7, whose deenergization permits the display of supervisory signal 9; while when subscriber C replaces his receiver, this act .is efi'ective to deenergize the relay 65 whose retracted armature 67, op.ens

-the before-traced circuit over conductors and 32 through relay 10 at D, whose armature is retracted and causes the display of supervisory signal 12. The falling back of armature 66 causes'tliesignal 68 to be displayed and the operator at H may now withdraw the calling plug of her cord from the jack, which will restore the apparatus to the right of condensers n and to normal by dc,- energizing relay 74, or sh e may wait until the operator at D, in response to the double display of the supervisory signals. withdraws the calling plu from the ack j, which act will beefi'ective, in addition to restoring the selective switch to normal, to deenergize the relay 70 whose retracted armature will then cause the display of the other supervisory signal 73.

The restoration of the selector switch F, .upon the withdrawal of the plug from the jack j, is effected as follows: On the opening of contact 19-21, the circuit before traced, extending over conductors 33 and 86 through relay RR, is interrupted at contact .21, relay RR is deenergized, and its retracted armature closes circuit from ground through the left armature of relay 54,.through operating relay OR to battery B, which relay OR is energized to place the talking wipers 49 and 51 uponopen circuit and to close a circuit for magnet 59 and generator G. Inasmuch as-relay 54 is locked, as before described, to ground at ofi-normal contact ON. the circuit through the operating relay OR will continue closed until the switch is driven by magnet 59 in the same direction as that in which it was operated to a normal position, at which time the denergization of relay 54, following the opening of contact ON, will permit the operating relay to fall back and the switch come to rest, ready to'be started again by the distributor switch E after the said switch E shall have selected it. As soon as relay OR attracts armature 56, the locking circuit for relay 26 is opened and the relay deenergized and all apparatus associated with the circuit of jack and with the selective switch F is then at normal.

Referring to Fig. 2, the mechanical structure .therc illustrated is provided with ref erence characters corresponding to those of the circuit at F. This is also true of Figs. 3, l and 5. I have illustrated the switch as arranged for twenty operative contact sets 46, 4.8,,and 50. 'lhere are in the said Fig. 2, however, shown, in all, twenty-one contact sets, but it will be understood that when the structure of'Fig. 2 is employed for the purposes of the switch shown at F in Fig. l, the first contact'set atthe left will be left disconnected. The additional contact is shown because when the switch is used as a distributer switch E, the wiper is always engaging an operative contact. chanical structure of Fig. 2, the instrumentalities, shown for the sake of clearness as wipers in Fig. 1, are represented by the common strips 47, 49, 51 and 53, which extend around respectively beneath their contacts 46, 48, 50 and 52, the said common strips forming the true terminals of the circuits of the switch in the same manner, that the.

wipers do in Fig. 1, while the wipers shown in Figs. 2 and 55, designated 4-7, 49, 51, and 53, have in themselves no circuit connections but serve. merely to cross the common strips to successive contacts 46, 48 and 50, respectively associated with them.

The stationary contacts, as clearly shown, in Fig. 2, are arranged in an arc of one hundred and twenty degrees, the contact terminals and their respective commons being superposed and insulated one from theother in a rigidly supported bank mounted upon main frame 95. Carrying the wipers 47 4-9251 and 53: which are three-pronged, the

prongs extending at angles of one hundred and twenty degrees so that one will be leaving the arc of the bank as another' is about to enter the said are, is a shaft 93, suitably journaled to the main frame 95 and to a cross-bar supported by the posts 99 and 100. Tothis shaft 93, is fastened also the ratchet 92, adapted to be engaged by pawl 91 carried by the armature 90 of magnet v5-9, which pawl, an successive actuations of themagnet, drives the ratchet, carrying with it shaft and wipers, step by step. The stop 102 is provided for pawl 91, so that a definite limit is fixed to the extent to which a thrustof the pawl may move the ratchet. Three normal positions exist for the switch of Figs. 2 and 3. That is to say, when any one of the three wipers 47" leave the arc of the contacts, one of the three studs 94, 94 or 94*, carried by ratchet 93, will come to engage the off-normal spring ON to hold it free from contact with its associated contact,'whereby the travel to normal of the switch F, as indicated in connection with Fig. 1, is stopped. When the In the me-* switch is in any of its normal positions, it will be understood that one or another of the three studs, carried by ratchet 92, will be in a position to hold spring ON from ongagement with its contact; but that the first actuation of magnet 59, lf6Ct l11g 2L thrust of pawl 91, will move the ratchet, by turning it one step, to a position where whatever stud may have been engaging spring ON, will be moved out of supporting relation therewith and the off-normal contact closed.

In Fig. 4k is shown a view of the private wiper 51, the private common 51 and the private contacts 50, the insulation being shown as cut away to disclose the relation of the parts. hen the private wiper is in the position shown in Fig. 4that is, operatively engaging and resting squarely upon one of the contacts 50then the wiper 53 of Fig. 5 will be in the position there indicated; that is, one such that it fails to cross the common strip 53 to one of the projections of the strip 52. It will be seen, however, that on a very slight movement of wiper 5l to the right from the position indicated in Fig. 4, wiper 53 will engage a projection of the strip 52; and also that when the wiper 51 has traveled for enough toengagethe middle contact 50 of Fig. 4 and to just disengage the contact 50 at the left, ,then the wiper 53 will still be engaging a projection of the strip 52 and will continue in such engagement until the wiper 51 has practically attained its fulloperative position engaging squarely the middle contact 50; it being understood, of course, that-the wipers 51 and 53 are mounted directly above each other upon the shaft 93. By the intermediate spacing indicated in Figs. 4 and 5, it is clear that each projection of the strip 52 serves to protect, inthe manner hereinbefore described, the wiper 51' from a partial step for one certain step inythe operation of the switch, during the period existing .l,etwecn when the wiper leaves one private contact 50 to the time when it reaches its full operative posi tion with respect to the next contact 50.

In the employment of the mechanical structure shown in Figs. 2 to 5 'for the distributer switch shown at IE, it will be understood, of course, that theoff-normal switch spring ON is dispnsed'with and one of the wipers .andits associated contacts and common may be left disconnected.

Itwill be understood that the structures of the figures described are merely for the purpose of indicating one form of mechanism to which my invention may be applied, but that the said invention is not to be in any way restricted to the specific mechanism in association with which I have illustrated and described it, or to the specific electrical circuit associations in connectionwith which I have applied it. -While I have in Figs. 1 and. 3 illustrated the protective projections might be made without departing fromthe spirit of my invention, and

lt'hat I claim .as new and desire to secure by Letters Patent of the United States is as follows 1. An automatic selecting system 1ncluding a selective switch stationary switch con-- tacts included therein, means for rendering some of said switch contacts busy, other s'ta tionary switch contacts positioned intermediate of said first-mentioned contacts, a stepping magnet for said switch, means for initially actuating said magnet controlled over said first-mentioned contacts when busy, and circuit connections for said lastmentioned contacts effective after initial actuation of said magnet toinsure complete actuation thereof. a

2. An automatic selecting system including a selective switch, stationary switch contacts included therein, means for rendering some of said switch contacts busy, other stationary switch contacts positioned intermediate of said first-mentioned contacts, a stepping magnet for said switch, a primary operating circuit for said magnet controlled by the idle or busy conditions of said firstmentioned contacts, and a secondary operating circuit-for said magnet controlled by said other stationary contacts effective on deficient operation of said primary circuit.

3. An automatic selecting system including a selective switch, stationary switch contacts included therein, means outside of said switch for rendering some of said switch contacts busy, a testwiper for said switch adapted to engage said contacts, an operating relay energized over circuits including said wiper and successive busy contacts, an operating magnet for stepping said wiper, an operating circuit therefor including a front switch contact of said relay, means for denergizing said relay as soon as said wiper engages an idle contact, and a circuit for said magnet including a back contact of said relay eifective on deenergization thereof to cause said magnet to complete a partially effected step of said wiper.

4. Arr automatic selecting system including a selective switch, a movable contact therefor, stationary contacts adaptedfor en gagement thereby, a stepping magnet for effecting travel of said switch, an operating relay controlled over circuits including said movable contact and successive stationary contacts, a second movable contact for said switch, stationary contacts for engagement thereby, said contacts being op'eratively po- I sitioned intermediate of said first-mentioned contacts, and two operating circuits for said 1 magnet, one including a front contact of said relay, the otherincluding aback contact thereof, one of said last-mentioned contacts and said second movable contact.

combination with a selective switch having l stationarycontacts and a traveling contact, I of an operating magnet therefor, a relay for controlling the same sensitive to the elecl trical conditions ofsaid contacts auxiliary Icontacts inter-spacing said first-mentioned contacts, twocircuits for said magnet, one I eluding an auxiliary contact, and means operated by said relay cont-rolling both said circuits, including a contact closed when the relay is inert and a contact closed when the relay is operatedfor completing said circuits respectively.

6. An automatic selecting system includ- .cluded therein normally unselectable in character, means for rendering some of said switch' contacts selectable, auxiliary switch contacts included in said selective switch and an adjusting magnet for said switch, means for initially actuating said magnet controlled over said first-mentioned contacts and circuit connections for said auxiliary contacts effective to insure complete actuation of said magnet-.'

7. .An automatic selecting system including a selective switch, normally unselectable switch contacts included therein, means for rendering some of said contacts selectable, auxiliary switch contacts associated with said firstmentioned contacts, a stepping magnet for said switch, a primary operating circuit for said magnet controlled by the electrical conditions of said first-mentioned contacts, and a secondary operating circuit for said magnet controlled by said auxiliary contacts effective on improper operation of said primary circuit.

8. An automatic selecting system includmg a selective switch, multiple switch contacts included therein normally unselectable in character, means outside of said switch for rendering some of said switch contacts, selectable, a test wiper for said switch. adapted toengage said contacts, an operating relay energized over circuits including said wiper and successive unselectable contacts, an operating magnet for stepping said wiper, an operating circuit therefor including a front contact of said relay, means for (leencrgizing said relay as soon said wiper engages a selectable contact and a circuit: for said magnet including a hack contact of said relay effective on de'encrgimttion,thereof to ca use said magnet to complete a partially cffected step of said wiper. I

i 9. The combination with a step-by-step including. a stationary contact, the other in.

ing a selective switch, switch contacts in 5. In an automatic selecting system, the

f t as switch of. an electromagnet controlling the stepping thereof, a principal operating circuit for said magnet, an auxiliary operating circuit therefor, and means for rendering said last-mentioned circuit effective only when on operation of said first-mentioned circuit an interstep position of said switch is assumed. l

10. The combination with a selective switch, of switch adjusting mechanism controlling step by step travel thereof, and means, for causing a re-operation of said mechanism to complete a step, effective when on initial operation of said mechanism an interstep position of said switch is assumed.

11-. The combination with a selective switch, of switch adjusting mechanism controlling step by step travel thereof, circuit connections for controlling said mechanism, and means for automatically rendering said connections effective to cause a re-operation' of said mechanism to complete a partially made step.

12. The combination in a selective switch with a switch adjusting ratchet and a controlling pawl therefor, of means for automatically reoperatingfsaid pawl when a partial switch step is made.

13. The combination in a step-by-step selective switch with principal electromagneti' cally operating means, of an auxiliary circuit for said means for preventing said switch from remaining inan interstep position.

14. The combination in a selective switch with multiple contacts, of means for automatically stepping said switch to select contacts' in a particular electrical condition, and auxiliary circuit connections serving to prevent said switch from remaining in an inter step position.

15. In a step-by-step selective switch, the combination with principal electromagnetically operating means, of main contacts and wiper, auxiliary contacts and wiper, and an auxiliary circuit for said operating means closed through said auxiliary contacts for preventing said switch from remaining in an interstep position.

In witness whereof, I hereunto subscribe my name this' lth day of May, 1907.

FRED SCHOENVVOLF.

\Vitnesses G. E. J. G.

MUELLER,- KELLooo.

Copies of this patent may be obtained for five centseach, by addressing the Commissioner of Patents, Washington, D. C. 

